A new ITER magnet in the spotlight

Working on the terminations of one Double Pancake of Poloidal Field coil 6, ASIPP, China.

Five of the six Poloidal Field (PF) coils that will manage the shape and stability of ITER's powerful plasma are under Europe's responsibility. Four of them are being manufactured in F4E's facility located on the ITER construction site and another is being fabricated in ASIPP, The Institute of Plasma Physics of the Chinese Academy of Sciences in Hefei, following an agreement between Europe and China.

It's Saturday morning and the streets are jammed. The ASIPP facility is a 40 minute drive from the centre of Hefei, a small town for Chinese standards of nearly 7 million inhabitants. As we make our way to the outskirts, the scenery changes and becomes less metropolitan. Eventually we find ourselves at the doorstep of the facility where ITER's sixth PF coil is being produced. The landscape and the river nearby may give you the impression that we are here for a walk. Yet the noise coming from the different manufacturing stations of the facility suggests that a team of 80 people has started their shift at 08:30 am and it hasn't been exactly a walk in the park.

The progress of PF6 is impressive. It consists of 9 double layers of superconductor, known in the ITER jargon as Double Pancakes (DP) because of their shape, which need to go through various fabrication steps. One of the first steps is winding the conductor with extreme accuracy to achieve the geometry of the coil. Around 30% of the entire coil has been successfully wound. If we were to cluster the main manufacturing activities of the DPs in four main steps these would be: winding, insulation, the manufacturing of the joints where cold Helium and current will be injected to make them superconducting, and vacuum pressure impregnation, where any air left in the component is removed and epoxy resin is carefully injected, and then cured to make it solid.

Crane lifting a Double Pancake of Poloidal Field coil 6 in order to be placed
on another station, ASIPP, China.

The winding
of a new DP is about to start, making it the fourth in a row to undergo this
process. The terminations of two DPs have been completed and the first DP is in
its final stage of vacuum pressure impregnation. It will soon move to the
stacking station so that the second DP goes through impregnation. “It’s a
sequential process that requires very good co-ordination so that one component
moves to the station of the other. The collaboration with the team here is
excellent. We are learning by doing and they are extremely committed to this
task” explains Carlo Sborchia, F4E’s PF6 Responsible Officer, who spends half
of his time in Hefei. Peter Readman,
F4E’s Technical Officer, who is there a quarter of the year, is commenting on
the excellent results of the termination works. “You will hear a lot of talk about
this because it is an extremely delicate technical task and the results have
been very good! If we don’t get the joints right, where the Helium and current
will flow in the magnet, they will quench and this would be a massive setback
in operation” he explains.

Working on the joint terminations of one Double Pancake of Poloidal Field coil
6, ASIPP, China.

After
impregnation, one DP gets stacked above the other until all nine are impregnated
together as one piece. Parallel to the manufacturing of the DPs, the ASIPP engineers
are testing with mock-ups the next fabrication steps, in order to be ready to
proceed with the real component. The next step for the mock-up will be to
undergo full coil impregnation.

It’s
remarkable how dedicated all teams are. This is how real collaboration is meant
to be building side by side a powerful magnet. There is a sense of pride in
being part of the biggest energy project that could make history. And this is
worth any given Saturday.